A surface-emitting unit including a surface-emitting panel as a light source has recently attracted attention. The surface-emitting unit is not limited to a lighting apparatus but used also for a backlight for a liquid crystal display, a computer monitor, or an outdoor advertisement such as a digital signage. In general, a surface-emitting element such as an organic electroluminescence (EL) element is used for the surface-emitting panel. The organic EL element can obtain a high luminance with low power consumption, and exhibits excellent performance also in terms of responsiveness and lifetime.
Since it is necessary to seal a surface-emitting element and connect a line to a surface-emitting element in a surface-emitting panel, a non-light-emitting region is located around an outer edge of a light-emitting surface of the surface-emitting panel. In order to achieve a large area of a light source with a small number of panels, arrangement of surface-emitting panels without contact with each other is preferred. In that case, a gap is produced between surface-emitting panels and this gap is also a site not emitting light.
Therefore, in a surface-emitting unit including a plurality of surface-emitting panels, lowering in luminance in a front direction in a portion corresponding to a non-light-emitting portion and a periphery thereof is inevitable. Therefore, without any measures being taken, such lowering in luminance appears as variation in luminance and a dark portion may be produced along the non-light-emitting portion.
Japanese Laid-Open Patent Publication No. 2005-353564 (PTD 1) discloses the invention relating to a lighting apparatus. This lighting apparatus includes a surface-emitting device and an optical member. This publication states that recognition of a dark portion caused by a non-light-emitting portion is less likely according to this lighting apparatus.
Japanese Laid-Open Patent Publication No. 2005-158369 (PTD 2) discloses the invention relating to a lighting apparatus. This lighting apparatus includes an optical member and a plurality of light-emitting elements. This publication states that illumination light can be emitted with less variation in luminance over a wide area from a front surface of each light-emitting element by using the plurality of light-emitting elements with this optical member and the lighting apparatus.